The ever-increasing prevalence of bacteria harboring extrachromosomal elements or plasmids that confer resistance to chemotherapeutic drugs, that specify production of surface antigens, hemolysins, bacteriocins, toxins and other invasins and/or that alter biochemical traits so as to make clinical identification difficult, is causing curtailment of bacterial infectious diseases to be increasingly more difficult and therefore constitutes a threat to the public health. The objective of our research is to study transmission and functions of plasmids in gram-negative bacteria so as to be able to develop means for effective control and treatment of bacterial diseases. Most of the research will be concerned with R plasmids in Escherichia coli and Salmonella typhimurium and will utilize minicell-producing strains of both of these bacterial species. During the coming year, we will specifically investigate: a) possible mechanisms for the evolution of plasmid replicons; b) mechanisms for establishment of conjugationally transferred plasmid DNA; c) the relationship between chromosome and plasmid replication in synchronously dividing populations of bacterial cells; d) mechanisms for amplification of the drug-resistance phenotype in R plasmid-containing strains; e) the configuration of plasmid DNA in minicells as it relates to expression of plasmid functions; f) protective immunity conferred by vaccination of mice with plasmid-containing Salmonella minicells; and g) functions of plasmids in gram-negative pathogens isolated from patients with septicemias. We will utilize the technologies of microbial genetics, molecular biology, immunology and electron microscopy in this research. BIBLIOGRAPHIC REFERENCE: Curtiss, R., III, D. A. Pereira, J. C. Hsu, S. C. Hull, J. E. Clark, L. J. Maturin, Sr., R. Goldschmidt, R. Moody, M. Inoue and L. Alexander. 1977. Biological containment: The subordination of Escherichia coli K-12. In: Proceedings of the Tenth Miles International Symposium. In press.